Add player stats, in-table ranking, host seating and review return

- Stats page (/stats): play style radar (TAG/LAG/rock/fish), VPIP, PFR,
  ATS, 3bet, WTSD, W$SD, WWSF, per-street fold rate, aggression
  frequency, hand win rate and net in BB, per table type, each with a
  bands-and-explanation sheet. Hands are counted per human player when
  they finish and stored as totals under data/stats/, keyed by a hash
  of the player ID (sent in a POST body, never in the URL).
- Ranking sheet at the table: everyone seated, ordered by stack or by
  net (stack minus buy-ins), updating live.
- The host can reorder seats by dragging (with a mini table preview and
  shuffle). Takes effect immediately between hands, otherwise at the
  start of the next hand; the dealer button stays with the same player.
- The full-session review opens in the same tab and its back button
  returns to the table it was opened from.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/stats/store.js

@@ -0,0 +1,115 @@
+'use strict';
+
+// プレイヤーごとの統計の保存先（data/stats/<プレイヤーIDのハッシュ>.json）。
+// プレイヤーID（ブラウザの localStorage にある席のトークン）はそのまま残さず、SHA-256 の先頭で名前を付ける。
+// 中身はテーブルの種類ごとの回数の合計だけで、ハンドの内容は持たない。
+// 同じプレイヤーの読み書きは順番に行う（ハンドが続けて終わっても数え漏らさない）
+const fs = require('fs');
+const path = require('path');
+const crypto = require('crypto');
+
+const DIR = process.env.STATS_DIR || path.join(__dirname, '..', '..', 'data', 'stats');
+const MODES = ['chips', 'friends', 'cpu'];
+// 続けて遊んでいるとみなす間隔（前のハンドの終わりからこれ以内に始まったら、間の時間もプレイ時間に入れる）
+const CONTINUOUS_MS = 3 * 60 * 1000;
+
+const queue = new Map(); // key → 直前の読み書きの Promise
+const cache = new Map(); // key → 中身（読んだもの・書いたもの）
+
+const keyOf = (token) => crypto.createHash('sha256').update(String(token)).digest('hex').slice(0, 32);
+const fileOf = (key) => path.join(DIR, `${key}.json`);
+
+const streets = () => [0, 0, 0, 0];
+function emptyBucket() {
+  return {
+    hands: 0,
+    won: 0,
+    preflop: 0,
+    vpip: 0,
+    pfr: 0,
+    atsOpp: 0,
+    ats: 0,
+    threeBetOpp: 0,
+    threeBet: 0,
+    sawFlop: 0,
+    showdown: 0,
+    showdownWon: 0,
+    wonSawFlop: 0,
+    seen: streets(),
+    folds: streets(),
+    actions: streets(),
+    aggressive: streets(),
+    netBB: 0,
+    ms: 0,
+  };
+}
+const empty = () => ({ version: 1, firstAt: null, lastAt: null, modes: {} });
+
+async function load(key) {
+  if (cache.has(key)) return cache.get(key);
+  let data;
+  try {
+    data = JSON.parse(await fs.promises.readFile(fileOf(key), 'utf8'));
+    if (!data || typeof data !== 'object' || !data.modes) data = empty();
+  } catch {
+    data = empty();
+  }
+  cache.set(key, data);
+  return data;
+}
+
+async function write(key, data) {
+  await fs.promises.mkdir(DIR, { recursive: true, mode: 0o700 });
+  const tmp = `${fileOf(key)}.tmp`;
+  await fs.promises.writeFile(tmp, JSON.stringify(data), { mode: 0o600 });
+  await fs.promises.rename(tmp, fileOf(key));
+}
+
+// 同じ key の処理を順番に行う
+function serial(key, fn) {
+  const prev = queue.get(key) || Promise.resolve();
+  const next = prev.then(fn);
+  const settled = next.catch((err) => console.error('[stats] 保存に失敗しました', err.message));
+  queue.set(key, settled);
+  settled.then(() => {
+    if (queue.get(key) === settled) queue.delete(key);
+  });
+  return next;
+}
+
+function add(bucket, entry, ms) {
+  bucket.hands++;
+  for (const k of ['won', 'preflop', 'vpip', 'pfr', 'atsOpp', 'ats', 'threeBetOpp', 'threeBet', 'sawFlop', 'showdown', 'showdownWon', 'wonSawFlop']) {
+    if (entry[k]) bucket[k]++;
+  }
+  for (const k of ['seen', 'folds', 'actions', 'aggressive']) {
+    for (let i = 0; i < 4; i++) bucket[k][i] += entry[k][i] || 0;
+  }
+  bucket.netBB = Math.round((bucket.netBB + entry.netBB) * 100) / 100;
+  bucket.ms += ms;
+}
+
+// 1ハンド分を足す。startedAt / endedAt はハンドの始まりと終わりの時刻
+function record(token, mode, entry, { startedAt, endedAt }) {
+  if (!MODES.includes(mode)) return Promise.resolve();
+  const key = keyOf(token);
+  return serial(key, async () => {
+    const data = await load(key);
+    // プレイ時間: ハンドの長さ。前のハンドから続けて遊んでいれば、間の待ち時間も入れる
+    const continuous = data.lastAt != null && startedAt - data.lastAt >= 0 && startedAt - data.lastAt <= CONTINUOUS_MS;
+    const ms = Math.max(0, endedAt - (continuous ? data.lastAt : startedAt));
+    if (!data.modes[mode]) data.modes[mode] = emptyBucket();
+    add(data.modes[mode], entry, ms);
+    if (data.firstAt == null) data.firstAt = startedAt;
+    data.lastAt = endedAt;
+    await write(key, data);
+  });
+}
+
+// 書き込み中のものを待ってから返す
+function get(token) {
+  const key = keyOf(token);
+  return serial(key, () => load(key));
+}
+
+module.exports = { record, get, emptyBucket, MODES, DIR };